Described below is a breaker device for low-voltage applications with at least one fixed contact and at least one movable contact.
Breakers for low-voltage applications are known for example from DE 10 05163 C1, DE 200414892 36 743 44 25 330 A1 or EP 04 50 104 B1. They consist of at least one fixed contact and at least one movable contact with associated drive, which is able to be actuated either in particular electrically or also magnetically and is activated by a specific algorithm. In DE 197 29 599 C1 triggering criteria on the basis of current (I) and current steepness(di/dt) are described, with an advantageous evaluation algorithm being derived from these values.
In known low-voltage power circuit breakers, the main contacts are usually opened via a mechanically operating switching lock. This can be tripped manually at the actuation level—or also automatically by thermal, magnetic or electronic actuators, if these detect an overcurrent. The operating times of the switching lock lie in the range of several ms, so that even in the case of larger short circuits the available electrodynamic forces from the current loop do not lead directly to contact opening, but are initially only directed against the forces of the locked switching lock.
Electronic short circuit breakers can be equipped with what is known as an “electromagnetic bypass” in order to bring about fast actuation with large short circuit currents.
Previously efforts have been made to resolve the problem in a better way than the above-mentioned triggering chain by creating an additional pivot point using an additional support, which however holds the contact closed temporarily with additional springs or guides. Only with extreme currents can electrodynamic forces overcome these spring forces and also bring about a temporary or final opening of the contacts without the aid of a switching lock.
The dimensioning of the switching device must however insure that the switching lock unlocks if there is a fault in the short circuit actuator. In the individual case a different triggering chain can be selected.
After execution of the dynamic processes the main contacts remain open. Many devices also allow temporary opening without there being a final forced opening by the lock.